P Plot

Overview

The P plot is a hybrid of the nested pixel and modified Whittaker plots. The basic idea is to be approximately the same size, have three levels of nesting, have a scattered arrangement of subplots, and to be representative of an area similar to the nested pixel and Modified-Whittaker plots. In addition, this plot incorporates the idea of square subplots scalable to a satellite photo pixel and is always oriented North. The P plot measures 30 meters on a side (30m x 30m or 900). Nested within are ten 1 (1m x 1m) plots, two 10 (3.16m x 3.16m), and one 100 (10m x 10m)

From the origin (0,0), walk out 100m tape (tape “1”) to 30m at 2700 (or west). This SW corner is point (30,0). When walking out tape, be careful to walk on the left (outside) side of tape to avoid trampling subplots along inside of tape. (Note: it is advisable to walk “wide” left with the tape and at 30 meters line up tape using back-azimuth with previous point to ensure no disturbance of subplots.)

From point (30,0), lay out the tape another 30 meters to 60m at 00 (or north). This NW corner point is point (30,30). Take same precautions as above to avoid nested subplots.

From point (30,30), lay out tape another 30 meters to 90m at 900 (or east). This NE corner point is point (0,30). Take same precautions as above to avoid nested subplots.

From point (0,30), run first 50m tape (tape “2”) 30 meters south (1800) to origin (0,0). This encloses the 900 P-plot. Again, take the same precautions as above to avoid disturbing subplots.

From origin (0,0) measure 14.14 meters at 3150 azimuth (NW) to origin of nested C-plot (10,10). To avoid trampling subplots, walk “wide” right of point (10,10). Follow similar procedures as above to properly identify point (10,10).

From (10,10), run second 50m tape (tape “3”) 10 meters to point (20,10) on 2700 azimuth. Take care not to stand in a subplot. (Note: there are four 1m2 subplots situated along the outside of nested C-plot. To avoid standing in one while you are setting up C-plot, walk wide right initially, and before 10m, walk wide left. Follow above procedures for identifying point.)

From point (20,10) walk tape another 10 meters along 00 azimuth to point (20,20). To avoid disturbing 1m2 subplots, follow procedure noted in step 7.

From point (20,20) walk tape another 10 meters along 900 azimuth to point (10,20). To avoid disturbing 1 subplots, follow procedure noted in step 7.

From point (10,20) walk tape another 10 meters along 1800 azimuth to point (10,10). To avoid disturbing 1m2 subplots, follow procedure noted in step 7. This encloses the C-plot.

Two 10 plots are set up in the (0,0) (B-plot) and (30,30) (A-plot) corners, respectively. Both plots are 3.16 meters on a side. Thus the outside corners of the B-plot are located at (0,0), 3.16m of tape “1” (aka “1-3.16m”) and 26.84m of tape “2” (2-26.84m). The outside corners of the A-plot are 56.84m of tape “1” (1-56.84m), point (30,30), and 63.16m of tape “1” (1-63.16m). These plots are set up while sampling.

The 10 1 subplots are located at fixed points along each tape. There are six “outside” subplots and four “inside” subplots. The “outside” subplots are located along the inside of the P-plot at locations (tape-distance from tape origin) 1-18m, 1-36m, 1-54m, 1-72m, 1-89m, and 2-18m. The “inside” subplots are located on the outside of the C-plot at 3-0m, 3-10m, 3-20m, and 3-30m. These subplots are setup while sampling.

Methods

The ten 1 subplots are sampled the most intensively. For each subplot, all unique biological crusts (optional), plant species, and abiotic cover types are identified. Biological crusts are categorized based on development and for each cover type, percent cover (foliar, basal, or both) is estimated within the subplot. Average height within subplot is also estimated for each plant species. For both 10 subplots (B- and A-plots) and 100 C-plot, presence of all biological crusts, plant species and abiotic cover types is recorded. Neither cover nor height is estimated. The P-plot is only searched for the presence of new (to plot) cover types and species. Again, neither percent cover nor height is estimated.